Technical Abstract:
A laboratory study was conducted to evaluate soil amendments for reducing ammonia emissions from open-lot beef cattle feedyards. A mixture of 1550 g of soil, 133 g of manure, and 267 g of urine were placed into plastic containers (20 cm x 20 cm x 12 cm depth). Using a vacuum system, clean air at a rate of 84.5 L/min was passed over the soil-manure surface and ammonia awas trapped by bubbling the air through dilute hydrochloric acid. Treatments consisted of a blank (soil with no manure), control (soil-manure mixture with no amendment), 4500 kg/ha A12(SO4)3 (alum), 9000 kg/ha alum, 375 kg/ha commercial product for reducing ammonia emissions (CP), 750 kg/ha CP, 4500 kg/ha CaC12, 9000 kg/ha CaC12, 9000 kg/ha brown humate, 9000 kg/ha black humate, 1 kg/ha of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), and 2 kg/ha NBPT. There were four replications of each treatment. Ammonia emissions were monitored for 21 days following application of the amendments. Cumulative ammonia emissions after 21 days expressed as a percentage of the control, were 0.4% for the blank, 8.5% for 4500 kg/ha alum, 1.7% for 9000 kg/ha alum, 73.6% for 400 kg/ha CP, 68.2% for 750 kg/ha CP, 28.8% for 4500 kg/ha CaC12, 22.5% for 9000 kg/ha CaC12, 32.4% for 9000 kg/ha brown humates, 39.8% for 9000 kg/ha black humates, 35.9% for 1 kg/ha NBPT, and 34.4% for 2 kg/ha NBPT. Results of these experiments suggest that ammonia emissions from open feedlots can be reduced using chemical additives. Cost-effectiveness and environmental impacts from the amendments should be evaluated before using these amendments in a commercial setting.